Antiemetics - 5-HT3 receptor antagonists Flashcards
Where in the brain is the vomiting centre and chemoreceptor trigger zone located?
1 - hypothalamus
2 - midbrain
3 - pons
4 - medulla oblongata
4 - medulla oblongata
- when stimulated the vomiting centre coordinates the vomiting response
The chemoreceptor trigger zone (CTZ) is sensitive to specific stimuli. Which of the following is NOT a receptor located on the CTZ?
1 - 5-HT3 (serotonin)
2 - D2 dopamine
3 - opioid (mu, kappa)
4 - neurokinin-1 (NK1)
5 - GABA
5 - GABA
- these receptors detect emetic agents
- the CTZ then stimulates the vomiting centre
Is the chemoreceptor trigger zone (CTZ) located inside or outside the blood brain barrier?
- outside
- important as the CTZ has a high density of 5HT3 receptors able to sense emetic substance that may otherwise not be able to cross the BBB
In addition to the vomiting centre and chemoreceptor trigger zone, the 3rd part of the vomiting response is called the vestibular nuclei. Where is this located in the brain?
1 - pons
2 - midbrain
3 - medulla
4 - cerebellum
1 - pons
- receives input from the labyrinth in the inner ear
- this is where motion sickness comes from
Which 2 of the following type of receptors are located on the vomiting centre?
1 - 5-HT3 (serotonin)
2 - D2 dopamine
3 - histamine H1 receptors
4 - muscarinic receptors
3 - histamine H1 receptors
4 - muscarinic receptors
What type of receptors are located on the vestibular nuclei that are able to receive stimulus from the labyrinth of the inner ear?
1 - 5-HT3 (serotonin)
2 - D2 dopamine
3 - histamine 1 receptors
4 - muscarinic receptors
3 - histamine 1 receptors
4 - muscarinic receptors
What is the normal communication pathway between the vomiting centre (VC), chemoreceptor trigger zone (CTZ), and the vestibular nuclei (VN)?
1 - VC to VN to CTZ
2 - CTZ to VN to VC
3 - VN to CTZ to VN or CTZ to VC
3 - VN to CTZ to VN or CTZ to VC
Our senses can trigger a vomiting reflex, which is trigger in the higher brain centres. Once stimulated which of the following do they stimulate to initiate vomiting?
1 - vomiting centre (VC)
2 - chemoreceptor trigger zone (CTZ)
3 - vestibular nuclei (VN)?
1 - vomiting centre (VC)
Which cells in the stomach are able to detect cytotoxic or other potentially dangerous products?
1 - parietal cells
2 - enterochromaffin like cells
3 - chief cells
4 - mucous cells
2 - enterochromaffin like cells
The enterochromaffin like cells of the stomach are able to detect cytotoxic or other potentially dangerous products in the stomach. What neurotransmitter are these cells able to release that ultimately will stimulate the vomiting centre?
1 - 5-HT3 (serotonin)
2 - dopamine
3 - glutamate
4 - GABA
1 - 5-HT3 (serotonin)
- specifically stimulates the vagus nerve
During a vomiting response, which of the follow occurs?
1 - lower oesophageal sphincter relaxes
2 - diaphragm and abdominal muscles contract
3 - intra-abdominal pressure increases
4 - autonomic response (tachycardia)
5 - epiglottis closes (reduce aspiration)
6 - all of the above
6 - all of the above
The vomiting centre co-ordinates the vomiting response. Which of the following pathways converge and stimulate the vomiting centre to elicit a vomiting response?
1 - vestibular system
2 - vagus nerve
3 - chemoreceptor trigger zone
4 - higher centres (sensory)
5 - all of the above
5 - all of the above
Which of the following is the core 5-HT3 (serotonin) receptor antagonists drug we need to know?
1 - Metoclopramide
2 - Chlorpromazine
3 - Ondansetron
4 - Cyclizine
3 - Ondansetron
What is the mechanism of action of Ondansetron?
1 - inhibit sensory information from reaching the vestibular nuclei
2 - inhibit 5-HT3 receptors on the vestibular nuclei
3 - inhibit 5-HT3 receptors of the vomiting centre
4 - inhibit 5-HT3 receptors on on chemoreceptor trigger zone
4 - inhibit 5-HT3 receptors on on chemoreceptor trigger zone
- may also act on peripheral 5-HT3 receptors in GIT and vagus nerve
Ondansetron is the core 5-HT3 (serotonin) receptor antagonists drug we need to know. This drug is indicated in nausea and vomiting due to a myriad of reasons including cytotoxic drugs, radiation and postoperatively. Why is this drug indicated in nausea and vomiting?
1 - 5-HT3 (serotonin) is the key neurotransmitter released in the GIT
2 - 5-HT3 (serotonin) has a maximal effect on the vagal nerve
3 - 5-HT3 (serotonin) is particularly sensitive to cytotoxic drugs
5 - 5-HT3 (serotonin) is effective at inhibiting the vestibular nuclei
1 - 5-HT3 (serotonin) is the key neurotransmitter released in the GIT
- no interaction with vestibular nuclei, so not effective in motion sickness